Darrich, I think you're thinking of a business contract, which is something else.
EJB=Enterprise Java Bean
WSDL=Web Service Description Language
The WSDL states what methods your webservice exposes, and how they should be called. It is therefore a contract between the server and the consumer.
To put it simply, contract-first means that you decide what you want before you actually code it, whereas contract-last means you decide it after you've coded everything.
You could compare it to the paradigm about writing unit tests before code; you define the results you want before you implement them. By extension, coding according to contract-first shows that you've thought about what is required of the webservice.
Contract-last, on the other hand, takes an ad hoc approach to web services; you write code to process and return some stuff, and then generate a web service from that.
This doesn't necessarily mean you have to write the required info in the WSDL before implementing the method, as long as you have documented what the WSDL will contain and end up writing exactly that into your WSDL. However, writing it beforehand helps to ensure you're actually implementing the right thing.
Writing a WSDL isn't hard, but it can be a bit time consuming, especially if you're not used to working with XML Schemas. Various tools exist to help with this.
You may want to read section 2.3 in
http://static.springframework.org/ (...)